The invention relates generally to axial flow rotary separators for agricultural crops such as grain of the type which may be included in a self-propelled combine harvester and more particularly to aerodynamic means which may be combined with mechanical means for conditioning at least a portion of the crop material passing from the separator to a cleaning shoe so as to increase overall separating efficiency and enhance the efficiency of the cleaning shoe.
It is known to divert part of the air delivered by a blower (whose main function is to provide an air blast for conventional reciprocating shoe) to engage a flow of crop material before it reaches the shoe to effect additional separation or preliminary cleaning. However, such known blower arrangements are associated with combines using a conventional transversely disposed threshing cylinder and grate with conventional straw walkers for separation, and which thus have the characteristic of maintaining uniform distribution of material across the width of the combine, or at least of not concentrating such flow with respect to lateral distribution. Such arrangements typically take the delivery of air from a restricted portion of the periphery of a centrifugal fan and subsequently split the air flow or in some cases two separate blowers are used.
U.S. Pat. No. 3,800,804, Boone, discloses a transverse flow fan, the output of which is split between a conventional cleaning shoe and a stream of crop material in which is combined the deliveries from a grain pan and straw walkers, with the object of effecting a pre-cleaning of that stream of material before it reaches a cleaning shoe. However, a disadvantage of this arrangement is that the crop material is already relatively concentrated so that an air blast has relatively less separating effect on it. It is also inherent in a transverse flow fan that part of the periphery must be reserved for an air inlet so that such fans are somewhat less flexible in applications where widely diverging air flow deliveries are required.
U.S. Pat. No. 3,603,063, Stroburg, discloses an attempt to take a part of the air flow from a cleaning shoe fan to provide an air flow between a threshing concave and a grain conveyor or grain pan beneath the concave so as to float some chaff and straw rearwards out of the machine and thus reduce cleaning shoe loading. However Stroburg discloses no means for concentrating the air flow in this area in a rearwardly directed stream.
It is also known in a self-propelled combine having a transversely disposed axial flow threshing and separating rotor above a conventional cleaning shoe, to divide the delivery from a transversely disposed transverse flow fan between the cleaning shoe itself and a flow of crop material from the separator which has been concentrated by suitable conveying and material handling means before being accelerated downwards.
However, the known prior art does not offer a blower arrangement particularly adapted to a combine having a fore and aft disposed axial flow separator operatively associated with a conventional cleaning shoe and designed to enhance the cleaning efficiency of the combination and help realize the relatively high volumetric efficiency potential in a combine having an axial flow rotary separator.